In recent years, many different intracardiac devices aimed at either repairing or replacing dysfunctional mitral valves have been developed. Examples of these include various cardiac valve support devices, the purpose of which is to provide a stable ‘landing pad’ for subsequently implanted prosthetic valves. Examples of such support devices may be in found in co-owned, co-pending WO 2012/031141 which discloses and teaches two-ring devices, as well as in WO 2013/128436 which relates to single-ring valve support devices. Both of these publications also teach two-stage methods for replacement heart valve implantation, wherein the first stage comprises the stable implantation of a support device, while the second stage comprises the delivery and implantation of a replacement valve within the central lumen of said support device.
One technical problem encountered in the use of all such devices is the need for said devices to remain in their intended position within or near to the mitral annulus, despite the fact that the contracting heart exerts displacing pressures in the order of 200 mmHg thereon. When the size of a typical stabilizing element is taken into account, said elements are subjected to forces of approximately 16 N. The design of adequate stabilizing (where “stabilization” refers to stabilization and/or anchoring and/or attaching to the heart) elements is further complicated by the fact that the operating environment of a device implanted within the mitral annulus is such that the displacing forces are not constant, but rather they are cyclical in nature. Consequently, said stabilizing and anchoring elements must be capable of withstanding high level stress forces, the magnitude of which changes rapidly, over both the short term (immediately after implantation) and over the long term (weeks, months and years) without succumbing to low and high cycle fatigue and subsequent crack formation and development to fracture.
While the list of possible stabilization strategies is—in theory—very long, there are various operative constraints that limit the selection of stabilizing means that may be used in practice. One such constraint is a limit on the dimensions of the stabilizing wings or arms that may be formed as part of the device, or attached thereto, in view of the fact that in most cases, it is highly desirable to deliver the intracardiac device to its working location in a minimally-invasive manner, such as by a transcatheter approach (for example, trans-apical, transseptal, transfemoral approaches). Such an approach requires that the device—including the stabilizing elements—be folded or ‘crimped’ to as small a crossing profile as possible, in order to facilitate packing within a delivery catheter that is itself small enough to pass through various blood vessels on its way to the deployment site at the mitral (or other cardiac) annulus.
Many prior art attempts at stabilizing crimpable mitral repair and/or replacement devices have been unsuccessful as a consequence of the contradictory requirements of a) a small crossing profile of the device, and b) sufficient robustness (i.e. size and material strength) of the device, in order to withstand displacing and fatigue-inducing forces, following deployment.
A pressing need therefore exists for new elements and strategies for the effective, long-term stabilization of devices such as replacement valves and their support structures at the mitral annulus, without interfering with the ability to crimp said devices to a size that is small enough to permit their packing into appropriately-sized catheters.
The present inventors have now developed new stabilizing and attachment element designs that meet this need.